1. Field of the Invention
The present invention relates to a freight pushing device especially adapted for use in a system for handling freight, as in a closed loop conveying system where palletized loads can be moved from one side of a freight dock to another.
2. Description of the Prior Art
There is in the prior art conveying devices used in the "merry-go-round" system which is found in use in present day freight docks, particularly in quite large freight docks. In such a system, there is a conveying chain which travels at or below the dock platform in an endless closed loop path between the loading and unloading sides of the dock, to move a plurality of wheeled carts in a closed loop. Each cart is provided with a "dog pin" which is engaged by one of a number of chain "dogs" positioned at regularly spaced intervals along the chain. As carts are loaded with freight and hooked onto the chain, they are carried to the other side of the dock, where the cart is released from the conveyor chain and unloaded. Subsequent to the unloading, the cart is again hooked onto the chain and carried back to the other side of the dock to be again loaded with freight.
One disadvantage of the conventional "merry-go-round" system described above is that its capacity is limited by the number of carts which it can carry at any one time. Since the empty carts must be returned to the opposite side of the dock, of necessity half of the conveying space along the endless chain is occupied by empties being returned to the loading side of the dock. Further, there is the problem that such carts when not in use can take up valuable space in the freight dock and otherwise impede operations. Another disadvantage of the system is that there is the initial expense of providing the wheeled carts adaptable to be carried along by the conveying chain, as well as the maintenance of the same.
Aside from the above described existing freight handling system and the pushing units associated therewith, there are in the prior art a variety of conveying devices and systems adapted for use in different types of operations. Typical of these are those shown in the following patents: Martin et al, U.S. Pat. No. 1,593,501; Shepherd, U.S. Pat. No. 1,856,733; Neal, U.S. Pat. No. 2,669,342; Timmons et al., U.S. Pat. No. 2,759,585; Peras, U.S. Pat. No. 2,990,941; Chasar, U.S. Pat. No. 3,182,823; Reighart, U.S. Pat. No. 3,269,501; McChain et al., U.S. Pat. No. 3,275,118; McCartney, U.S. Pat. No. 3,279,631; Lord, U.S. Pat. No. 3,333,675; Frey, U.S. Pat. No. 3,421,641; and Egeland et al., U.S. Pat. No. 3,447,665.